The present invention relates to electronic devices.
It is generally recognized that conventional VLSI integrated technical technology will be prevented from further scaling by the time MOS devices get down to a quarter micron channel length, and perhaps even at much larger geometries. Since much of the advance in integrated circuit capabilities has been based on the continued progress of scaling, this near-future barrier is of substantial concern.
Thus it is an object of the present invention to provide an integrated circuit technology wherein active devices can have active regions smaller than one quarter micron in dimension.
It is further object of the present invention to provide an integrated circuit technology wherein active devices can be fabricated which occupy a total area of less than 1/4 of a square micron average for each active device.
A further inherent limitation of conventional integrated circuit technology is speed. MOS devices have inherent limits on their speed due to the channel-length transit time. Intergrable bipolar devices also have inherent speed limitations, due to the base width transit time, and are also likely to have high power dissipation.
Thus it is an object of the present invention to provide an active device having higher potential maximum speed than any MOS device.
It is a further object of the present invention to provide an active device which is potentially faster than any bipolar device.
It is a further object of the present invention to provide an active device which is potentially faster than any bipolar device and which also has a very low power dissipation.
To achieve these and other objects, the present invention provides: a new genus of electronic devices, wherein at least two closely adjacent potential wells (e.g. islands of GaAs in an AlGaAs lattice) are made small enough that at least two components of momentum of carriers within the wells are discretely quantized. This means that, when the bias between the wells is adjusted to align energy levels of the two wells, tunneling will occur very rapidly, whereas when energy levels are not aligned, tunneling will be greatly reduced. This high-gain mechanism leads to useful electronic device functions.
A difficulty in making quantum-coupled devices into functional electronic circuits is that these devices are so extremely small that it is typically necessary to run a number of them in parallel to provide macroscopic output currents. In addition, the routing of wiring to couple into and out of these multiple parallel active devices is also difficult, since the tight geometry constraints of the devices place substantial constraints on the geometry which must be used for the wiring.
Thus, it an object of the present invention to provide a device structure using quantum-coupled devices wherein input and output connections to route macroscopic currents to and from the devices are provided.
According to the present invention there is provided:
An electronic device comprising:
a plurality of first and second potential wells each comprising an island of a semiconducting material having a minimum dimension less than 500 Angstroms and another dimension less than 1000 Angstroms;
a barrier medium interposed between said first and second wells wherein the minimum potential energy of carriers is at least 50 millielectronvolts higher than the minimum potential energy of carriers within said wells, said wells being physically separated by a distance which is less than three times the smallest physical dimension of either of said wells;
a first conductor electrically coupled to each of said first wells;
a second conductor electrically coupled to each of said second wells; and
an output contact laterally separated from plural ones of said second wells by said barrier medium, said barrier medium between said output contact and said second wells having a minimum lateral width which is no more than twice the minimum lateral width separating said first and second wells;
wherein each of said wells comprises a lightly doped semiconductor, and each said conductor comprises a heavily doped semiconductor.